1. Field of the Invention
The present invention relates to a chip information character set generation system used in a semiconductor device and a method of marking a chip of the semiconductor device with a chip information character set. More particularly, the present invention relates to a chip information character set generation system configured to generate a chip information character classifying semiconductor chips in a semiconductor device into superior goods and inferior goods and indicating information about the semiconductor chips, and a method of marking the semiconductor chips of the semiconductor device with the chip information character set.
2. Description of the Related Art
Generally, a semiconductor device is manufactured by unit processes such as a deposition process, a photolithography process, an etching process, an ion implantation process, a metal wiring forming process, etc. The unit processes are repeatedly performed on a wafer including a semiconductor material such as silicon so that a plurality of semiconductor chips is formed on the wafer.
Mostly, the unit processes are performed by the lot, consisting of 25 pieces of wafers, and a lot identification (ID) is granted to each lot. Additionally, the unit processes are performed and managed per each lot ID in a fabrication line for a semiconductor device. Thus, specific information, such as a current position or a processing state of a wafer, can be determined using the lot ID.
An electric die sorting (EDS) process is performed on a wafer that has been fabricated out, and on which semiconductor chips have been formed. In the EDS process, a pre-laser test is performed to determine a normality of the semiconductor chips on the wafer. In addition, a laser repair process is executed to restore chips among abnormal semiconductor chips. Then, a post-laser test is performed to determine a normality of the restored semiconductor chips. Finally, a test to determine a normality of the semiconductor chips is performed under conditions that are different from those of the pre-laser test and the post-laser test.
After the EDS process is performed, the semiconductor chips on the wafer are classified into superior goods and inferior goods. In an inking process, each semiconductor chip that has been classified as an inferior good can be indicated by marking a dot on a front face of the semiconductor chip. Then, a sawing process is performed on the wafer to divide the semiconductor chips formed on the wafer. Finally, a packaging process is performed to assemble each divided semiconductor chip that does not have a dot on the front face, thereby completing a semiconductor device.
However, information about each semiconductor chip can not be known after the divided semiconductor chips are assembled into the semiconductor package by the packaging process. Here, a position of each assembled semiconductor chip on/in a wafer can remain unclear, and an exact time and a manufacturing apparatus used to perform the processes on each assembled semiconductor chip can be also unclear. Furthermore, whether there were any noticeable reactions while manufacturing the semiconductor device can be unknown. As described above, an analysis of the semiconductor chips is rather challenging because a history of each assembled semiconductor chip is unknown. Thus, determining causes of defects of the assembled semiconductor chips can be difficult when the defects are generated or come to light.
In order to avoid the above-mentioned problems, there has been an effort to develop a process for writing information about each chip on a rear face of each superior good, instead of performing the inking process in which a dot is marked on the front face of each inferior good. This alternative method not only divides the semiconductor chips into the superior and the inferior goods, which can have been performed by the conventional inking process, but also writes a lot ID, a wafer number, and a coordinate of each semiconductor chip on the rear face of the each superior good, thereby enabling further access to the information about the semiconductor chips in the future. An example of a chip information character written on a rear face of a chip is described as follows.
P51841X01100100
Here, “P51841X” indicates a lot ID, “01” represents a wafer number, i.e., here the indicated wafer is a first wafer, and “100100” means a chip coordinate in the wafer. That is, here, the indicated chip is located at a coordinate of 100×100, all of which are used in a fabrication line for a semiconductor device. As shown above, when the chip information character includes the lot ID, the wafer number, and the chip coordinate in the wafer, the chip information character has a large number of characters, such as 11 to 15 characters.
Further, when a net die, i.e., a number of usable chips produced from a wafer, is great, the number of chips on each of which the chip information character is marked increases because the lot ID, the wafer number, and the chip coordinate in the wafer are marked on the rear face of each chip as described above.
Therefore, marking the lot ID, the wafer number, and the chip coordinate in the wafer on the chip requires much time, thereby decreasing a productivity of the semiconductor device.